Window structure for cathode-ray tubes



Nov. 11, 1952 A. BRASCH 2,617,953

WINDOW STRUCTURE FOR CATHODE-RAY TUBES Fi led June 28. 1949 .5 Shegts-Sheet 1 A J5] !!!!5 a II...

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I 88 69 ARNO BRASCH Nov. 11, 1952 A. BRAscl-l 2,617,953

I WINDOW STRUCTURE FOR CATHODE-RAY TUBES Filed June 28, 1949 3 Sheets-Sheet 3 ml [Ll] I LLLl INVENTOR I ARNO BRASCH Patented Nov. 11, 1952 UNITED STATES WINDGW STRUCTURE FOR CATHODE-RAY TUBES Arno Brasoh, Brooklyn, N. Y., assignor to Electronized Chemicals Corporation, a corporation of New York Application June 28, 1949, Serial No. 101,768

3 Claims.

This invention relates to high voltage corpuscular rays of large intensity and more particularly to discharge devices of the capacitron type. Such devices usually employ impulse type discharges for the production of corpuscular radiation which is not too homogeneous yet sufficiently penetrating; according to the voltage applied, to be used for a great number of industrial purposes such as the sterilization of perishable and other organic or inorganic matter.

In such impulse type discharge devices, the peak currents are rather large, for example of the order of 100,000 amperes or more, with the result that great mechanical and electrical strains are exerted upon the receiving parts of the device, especially the exit or window parts of a tube.

Another difficulty is to insure continuous and safe operation of the device with a minimum of repair and other adjustments and with the use of as little and as inexperienced help as possible or available in ordinary industrial establishments such as food processing plants.

As a result of electrical and mechanical strains, the exit or window parts may be destroyed, causing long work interruptions for the'replacement of parts and the reconstitution of the vacuum.

Up to-now radiation and the corresponding discharge devices have mainly been used for research, medicine and laboratory purposes where small beams and accurate focussing were foremost requirements.

Itis one of the objects of the invention to provide a large and relatively unfocussed beam of great intensity to permit radiation to be applied to as large an area as possible with sufiicient penetration and even distributionover the entire area and its cross section.

A. more specific object of the invention is a large window permitting the passage of such radiation with a minimum of loss and without undergoing excessive mechanical and electrical strain.

Another object. of the invention is to provide window structures which are safe in operation and yet if necessary may be easily and quickly A further object of the invention is to provide auxiliary window structures which if. broken or put out of operation, do. not interrupt production and more specifically do not prevent another or main window structure from operating thus assuring continuity of processing.

A still more specific object of the invention is a window structure wherein the window is in continuous or periodic motion.

In a particular embodiment of this arrangement, the motion is a translatory one and the window consists of a linear band passingthe path of the cathode rays in a linear planar movement of predetermined and usually rather slow speed.

In this connection, it is one of the principal objects of this invention to provide a sealing arrangement for tightening the tube sufficiently to permit continuous or discontinuous movement of the Window past the cross-section of the tube substantially without impairing the vacuum conditions existing inside the tube.

A more specific embodiment of this sealing arrangement is a feeding mechanism in the form of labryinth type grooves or channels extending in a direction both along and across the movement of the window band.

Another object of the invention is asealing arrangement including a liquid channel type seal surrounding the portions to be sealed during the movement of the window across the path of the electrons.

Still another object of the invention is the distancing of the auxiliary windows from the main window structure to assure safe and continuous operation in order to eliminate slow electrons and negative ions.

A specific object of the invention is to provide artificial cooling means on one of the auxiliary window structures thus relieving the main window structure from thermic stress.

Still anotherobject of the invention is to provide supporting grills for the different window structures in predetermined thickness relation so as to distribute and reduce the stresses on the different window structures and especially on the .main window structure.

ferred dimensions 1. e. Where the diameter of the window is of the order of or larger than the distance of the window from the cathode.

Figures 3 and 4 also in top and front views respectively illustrate schematically the cooperation of a main window structure with auxiliary outer and inner windows, i. e. windows arranged in the path of the cathode rays in front and behind the main window.

Figures 5 and 6 in top and front views, the latter in section illustrate the combination of two windows, one in front of the tube before the main window with the main window structure including as a window a continuous rolling metal band.

Figure 7 is another front view section.

Figure 8 shows schematically a flange seal including a liquid channel which may be used as a modification of or in combination with the sealing arrangement of Figures 5, 6 and 7.

Figure 9 shows diagrammatically an automatic feeding and sealing mechanism for a discontin-- uously moving window band.

Figures 10 and 11 show a sliding frame transport mechanism; and

Figure 12 represents a modification of the sliding frame in Figures 10 and 1'1.

In Figures 1 and 2 there is shown a main window structure such as disclosed in Patent 2,449,872 issued to A. Brasch et al. on September 21, 1948. However, any other window structure may be used in this connection without exceeding the scope of the invention.

In the main window structure shown, part I represents an aluminum foil forming the window which is provided with a self-sealing coating 2 and pressed between rubber rings 3 and 4 against flange 5 by means of a counter-plate 6. Flange 5 is formed on tubular extension 1 of a cathode ray tube (not shown) of the capacitor or shock discharge type.

Tubular extension I is attached over flange 8 to flange 9 of another and preferably coaxial tubular extension I of the cathode ray tube. Between flanges 8 and 9 there is inserted a metal ring II carrying, preferably welded thereto, another aluminum foil I2 forming the auxiliary window.

Both aluminum foils I and I2 are substantially of the same thickness.

The thickness of the window should preferably be such that not more than M or sometimes even less than of the intensity of the radiation is lost or absorbed. The diameter of the window or at least its planar extension is at least of the order of 5 inches, preferably 8 inches; in certain practical applications, planar extension of the order of 12 inches and more is employed.

The distance of the main window from the cathode is of the order of 40 inches for 4,000,000 vo s.

The vacuum in the tube should be good enough, for example of the order of millimeter, to assure sufficient free length of way for the corpuscular rays.

The window or windows may have any desired planar shape; they may be circular, elliptical, rectangular or of any other shape as required for the purpose of a particular application.

The window does not need to be flat. It may be curved as explained further below. If necessary it may be corrugated, the corrugations being sinusoidal or triangular in character.

Instead of aluminum, other material may be used without exceeding the scope of the invention; metals, such as stainless steel, or plastics such as polystyrene, or a mixture or a multi-ply bond of plastic and metal such as a Bakelite sheet provided with a metal powder layer, the latter preferably being applied by cathode bombardment in vacuum.

Any or all of the windows may be provided with rubber or other self-sealing layers such as disclosed in the Patent 2,449,872 referred to above.

Metal ring II has a disc-shaped extension I3 which is pressed through rubber rings I4, I5 between flanges 8 and 9. These flanges are pressed or stamped together in any known manner such as by screws.

Each or any of the windows I and I2 are supported by a grill such as disclosed in the patent to Brasch cited above and shown at I6 and II respectively, with the provision, however, that grills I6 and I1 may have different thicknesses, one preferably I1, being thicker in order to protect main window grill I6 from the impact of electrons.

The heat thus absorbed by window structure I2, I! is conducted over disc I3 and flanges 0 and 9 to the tubular extensions I and III.

In order to facilitate heat conduction cooling coils I8 are arranged around tubular extensions I and I0 and flanges I4 and I5.

The spaces provided between windows I and I2 and between window I2 and the tube proper are separately evacuated through exhaust systems connected to tubes I8, I9, respectively.

Figure 2' shows a modification of Figure 2 wherein the distance of the main window I from cathode I00 is made of the order of the diameter of the window. The window itself appears to be corrugated to insure greater mechanical strength and better heat convection, both dimensions for example, being of the order of 40 inches.

In another embodiment of the invention, which need not be further illustrated as obvious to the reader, the diameter of the window is at least twice the distance of the window from the cathode.

In Figure 2' there is also indicated an auxiliary window I2 with triangular corrugations. This window is arranged in the space between window I and cathode I00 and serves substantially a similar purpose as the corresponding window I2 in Figure 2.

Figures 3 and 4 show an additional or auxiliary front window 20 placed in front of main window I and in the path of the cathode rays passing window I. Front window 20 consists of an aluminum foil similar to those of windows I and I2 and is shown to be attached to a structure similar to that shown for main window I; however, if necessary, the front window 20 may be attached to the corresponding flange 2| of tubular extension 22 in a manner similar to that shown for window I2 without exceeding the scope of the invention.

Figures 5 and 6 show a main window structure including a window which is continually fed past the path of the cathode rays. In front of this main window there is an auxiliary window structure of the type shown in the patent to Brasch et a1. However, this auxiliary front window may be replaced without exceeding the scope of the invention by any other window such as a window of the type shown at I2 in Figures 1 and 2.

There also may be another or rear auxiliary window arranged behind the main window structure which may be either of the type shown in the patent to Brasch et al. or, preferably, of: the type shown at l2 in Figures 1 and- 2 in order to relieve electric as well as thermalstresses from main and front window structures;

Each or any of thesewindow structures may be provided with grill type supports asshown in the patent to Brasch et a1. cited above or such. as shown in Figures 1 and 2 at I l. The auxiliary grill structures may have the same thickness as the main grill structure or difierent thicknesses; preferably, the grill elements may becomethicker the closer the grill is arranged to the source of cathode rays.

In Figures 5 and 6, as already stated above; the main window is arranged to be fed past the path of the cathode rays. This main window is in the form of an aluminum band or ribbon 24 which is transported from a take-off reel 25- past the window' structure to a take-up reel 26. Take-up reels 25 and 26 are supported on the tubular extension 21 of a cathode ray tube. and are driven in a manner as'is well known from film transport and similar mechanisms.

The auxiliary front window structure 23 is supported on another tubular extension 29. The corresponding flanges 30, 3 of tubular extensions 21, 29 respectively, forming the main window structure, are attached to or clamped together by means of tightening screws 32 arranged regular- The ly along the periphery of the two flanges. flanges and 3| are spaced. by springs 33 surrounding the screw bolts 34 of screws 32 to insure suiiicient and adjustable tightening and sealing without interfering with the transport of ribicon 24.

The transport of ribbon 24 is effected by a number of rollers which are mounted in flanges 35 and 3 respectively There is a pair of front and rear rollers 35, 36 and 31, 38 respectively, which serve to draw the ribbon 24 into and out of the window structure formed between flanges 30 and 3|.

There also are four arrays of side rollers, two arrays being arranged on each side of the window opening 39. The two arrays of side rollers 40, 4|, respectively, serve to guide the extreme edges of the ribbon 24 past the window. The rollers of each of these arrays of side rollers 40, 4| are arranged as shown in Figure 5 alternatingly in the opposing flanges 30, 3| so as to provide a weaving path for the extreme edges of ribbon 24. This weaving path forms a labyrinth type channel which while facilitating transport of the band of the ribbon therebetween impedes the access of air to window 39.

Inaddition to this longitudinal weaving, another weaving path is provided along the axial extensionof rollers 40, 4| by providing grooves thereon such as are shown on some of the rollers in Figure 6.

Figures 6' and 7' also show two other arrays of side rollers 42, 43 respectively, which are also provided with grooves to form a transverse labyrinth. Side rollers 42, 43 are arranged to provide a straight path for window band 24 as shown in section in Figure 7. Thus the band 24 changes from a weaving path while engaging rollers 40, 4| at the extreme edges of the band, to a straight path while engaging rollers 42, 43 at amore central portion of the band adjacent the window opening39.

Inthis way it is. assured that ribbon 24 will pass the window opening 33in a relatively flatv position thus maintaining a maximum of electric'and thermicstability.

In order to enhance sealing conditions there may be provided an additional exhaust, shown at 44,. for the spaces between the rows of rollers 40 and 42, and the rows of rollers 4| and- 43, respectively.

All, or atleast some of the outer rollers 35, 36, 31, 38, 40 and 4| are provided with gears such as shown schematically at one end of their axis at in Figure 6. All or at least some of these gears are intermeshing to provide synchronous movement of the relatively thin (.010 inch) aluminum foil.

One-of. these rollerssuch as shown. at 36 is connected over a large gear wheel 46 and a small gear wheel 41 to a motor 48 attached to the outside of. tube extension 21.

The speed required is rather small and of the order of inches per hour, preferably 10 inches perhour of continuous speed.

This speed, of course, may be variable.

The spaces formed between windows 25 and 24 and between 24 and any preceding window, or the cathode ray tube proper, may be separately connected to the same or to different exhaust systems, parts of which are shown at 49 and 50, respectively.

FigureS shows a sealing mechanism which may be. used alone or in combination with the roller arrangement shown in Figures 5, 6 and 7 respec tively. This sealing arrangement includes a liquid or'semi-liquid seal surroundin flanges 52, 52 formed on tubular extensions of the cathode ray tube such asshown for example at 21, 29 in Figures 5 and 6. Attached to these flanges, there is a channel member 53 surrounding the flanges and forming a quadrangular or circular channel which is filled with fairly consistent oil, mercury or any other sealing liquid or semiliquid compatible with the window material such as is shown at 54.

The window may not only be of aluminum but of any other material of suflicient strength, structure and thinness such as stainless steel.

The ribbon 55- after having passed the path of the cathode rays extends between flanges 5-2, 52' provided with rubber gaskets 55, 51' through liquid 54 and through an opening 58 in channel member 53 which may be sealed against outside pressure by rubber gaskets or rollers 59, 50.

After having passed opening 58, ribbon 55 is passed between two rollers, one 6| formin a guide roller and another 62 forming. a driving roller drivenin turn by a motor (not shown).

After having passed or driven through rollers 61, 62. ribbon 55 is passed on. to a take-up reel (not shown).

Similarly on the other i. e. the entrance end. of flanges 52, 52', ribbon 55 is driven or drawn through entrance rollers. 64, 65 and entrance opening 66 of channel. 53 and through liquid 54 across the path of the cathode rays.

Flanges 52 52' are provided with greaseopenings. 61 closedv by screws or similar closure membars 68. To permit the grease or oil to facilitate gliding as well as sealing, rubber rings 55, 51 are also providedwith fine slots such as shown at 69..

Rings 55, 51 are curved to provide a curved path which may be convex or as shown a concave path 55- for band 55, thus ensuring flatness of the window during passage.

Otherwise during its passage across the oathode rays the: ribbon may be fed and supported in the manner shown or described in connection with Figures 5; 6 and 7 or in. any appropriate manner without exceeding the scope of this invention.

In order to facilitate the transport of the ribbon, the ribbon edges may be provided with perforations or other indentations and the transport rollers or at least some of them may be provided at the apporpriate points of engagement with dents, teeth or similar projections as is well known in the art of band transport mechanisms.

Figure 9 illustrates both schematically and diagrammatically a modified transport mechanism and circuit permitting instead of a continuous movement of the ribbon, a discontinuous movement of such window ribbon across the path of the cathode rays. The discontinuous movement has the advantage that it is not necessary to provide a, continuously moving yet airtight sealing mechanism such as shown in Figures 5, 6 and 7.

In this modified embodiment of the invention it is sufl'icient to tighten the flanges or other closure members forming the window, permanently and for a comparatively large period. During this period the window is continuously exposed to the cathode rays for a predetermined time or a predetermined number of discharges. After such predetermined time the flanges are temporarily and briefly relaxed so as to permit a quick displacement of the ribbon past the ray passage and the positioning and exposure of a fresh portion of the ribbon to the cathode rays. Thereupon, the closure members are again and permanently tightened and operation continues as before.

Thus, only during a relatively small period of time, for instance during a fraction of a second, the seals are relatively relaxed while during a relatively much greater period of time, for example, during a half hour, the seals are permanently tightened.

During the relaxation time of the seal, and practically synchronously therewith, or preferably also if necessary for a predetermined time after tightening, a pump mechanism is operated to compensate for the loss of vacuum incurred during the period of seal relaxation.

Accordingly, cathode ray bombardment may start immediately after seal relaxation or also if necessary a predetermined time thereafter,

i. e. after the vacuum necessary for operation has been reconstituted.

Figure 9 shows a seal relaxation mechanism as applied to any closure members as a pair of flanges 10, H formed on tubular extensions of a cathode ray tube such as shown in any of the preceding figures.

Flanges 10, 'H are made of soft iron or similar magnetizable and demagnetizable material and may be made of one piece or laminated as is well known in the art.

Each of the flanges 1B, H or at least one of them is provided with a magnetizable winding. The windings shown at 12, 13 are wound in opposite directions to increase magnetic attraction 6 other appropriate manner without exceeding the scope of this invention.

The opening and closing motions of the flanges 70, H and the corresponding current flow in windings l2 and 13 are controlled as shown diagrammatically by generator !8 which in turn is controlled by a pulse counter circuit 19 which also controls driving motor for the grooved feed rollers or any other driving members of the window ribbon.

Counter circuit 19 is also connected to control exhaust pump 8| for exhausting the subatmospheric spaces immediately behind or before window 1'! to compensate for the loss in pressure during the relaxation of seal mechanism 11,10,11.

The counter circuit 19 is controlled by shockdischarge generator 82 which in turn controls the cathode ray tube of a capacitron schematically indicated at 83.

The counter circuit shown diagrammatically at 19 is well known in the art and is adapted to operate after a predetermined number of pulse discharges, for a predetermined and preferably adjustable length of time sufficient to effect demagnetization of windings 12 and 13, separation of flanges 7i and H and passage of a predetermined portion of ribbon 1'! under the control of driving motor 80.

Simultaneously and if necessary also for a predetermined time thereafter, under the control of counter circuit [9, pump 8! is operated to make up for the loss in vacuum occurring during the seal relaxation time.

Remagnetization of winding '52 and i3 and rescaling of flanges 10 and H as well as opereration of the shock discharge generator 82 are also effected under the control of counter circuit 19.

The shock discharge operation of generator 32 may also be under the control of a vacuum gauge shown at 83 depending upon the reconstitution of a predetermined vacuum necessary for oper- *ation.

Counter circuit 19 may be replaced without exceeding the scope of the invention by a simple Well known multi-contact time or sequence switch which effects a desired number of switching operations in a predetermined time sequence.

After a predetermined length of time or a predetermined number of shock discharges the counter circuit or time switch 79 operates again and the entire cycle of demagnetization, driving and pumping operation is repeated in the abovementioned sequence or in any other sequences as desired in accordance with the processing operations required to be performed by the oathode ray tube, or capacitron diagrammatically shown at 83'.

The speed of the various driving motors shown in Figures 6 and 9 may be changed if necessary, manually or automatically to accelerate or retard operation in accordance with this invention and without departing from the scope thereof.

Figures 10 and 11 show a manual or semiautomatical window exchange device which may be used in combination with a sealing mechanism such as shown in Figures 8 or 9 or with any other type of closure members.

Two windows 84, 8t welded, screwed or otherwise attached to frames 85, 86, are placed, attached or simply pressed over corresponding openings 81, 88 of a holder 89 adapted to slide between gaskets 9B, 91 and flanges 92, 93 or other closure members of a vacuum tube or similar electron discharge device.

Holder 88 may be pushed between gaskets 90, 9| in one of two operating positions in which either window 83 or 83 is exposed to the oathode rays. While one of the windows is exposed, the other of course, may be replaced and thus continuous operation of the discharge device be maintained for any length of time.

Figure 12 illustrates a rotary replacement movement instead of the translatory movement illustrated in Figures 10 and 11. 94 indicates a disc-type holder of a number of windows 95. Holder 94 is rotated between gaskets and flanges such as shown at 90, 9|, 92 and 93 in Figures 10 and 11 to permit quick exposure and replacement of any number of windows in the path of the cathode rays.

Any sort of Window exchange mechanism and arrangement may be used for the purpose of the invention, without exceeding the scope thereof.

I claim:

1. In a discharge tube of the electron accelerating type, means forming a tube body with a cavity therein having an opening at one end, a continuous ribbon of electron permeable material, mounting and translating mechanism for positioning a portion of said ribbon across said opening and for advancing said ribbon across said opening, clamping means secured to said tube body at said opening for clamping against said ribbon around the periphery of said opening to seal said opening with said ribbon portion, means for releasing said clamping means to permit advance of said ribbon, and vacuum pumping means connected to said cavity for exhausting gas which may have leaked thereinto while said clamping means was released.

2. In a discharge tube of the electron accelerating type, means forming a tube body with a cavity therein having an opening at one end, a continuous ribbon of electron permeable material, mounting and translating mechanism for positioning a portion of said ribbon across said opening and for advancing said ribbon across said opening, clamping means secured to said tube body at said opening for clamping against said ribbon around the periphery of said opening to seal said opening with said ribbon portion, means for releasing said clamping means momentarily and for actuating said translating means to advance said ribbon during the interval when said clamping means is released, and vacuum pumping means connected to said cavity for exhausting gas which may have leaked thereinto while said clamping means was released.

3. In a discharge tube of the electron accelerating type, means forming a tube body with a cavity therein having an opening at one end, a continuous ribbon of electron permeable material, mounting and translating mechanism for positioning a portion of said ribbon across said opening and for advancing said ribbon across said opening, sealing means secured to said tube body at said opening for forming an airtight seal around said opening between said tube body and said ribbon, and vacuum pumping means connected to said cavity for evacuating said cavity.

ARNO' BRASCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,735,302 Slack Nov. 12, 1929 1,907,507 Coolidge May 9, 1933 1,937,849 Slack Dec. 5, 1933 1,941,157 Smith Dec. 26, 1933 2,010,712 Coolidge Aug. 6, 1935 2,030,492 Applebaum Feb. 11, 1936 2,094,103 Horsley et al. Sept. 28, 1937 2,187,126 Kern et al. Jan. 16, 1940 2,213,070 Farnsworth Aug. 27, 1940 2,327,586 Atlee Aug. 24, 1943 2,373,661 V De Phillips Apr. 17, 1945 2,429,217 Brasch Oct. 21, 1947 2,431,113 Glytes et al Nov. 18, 1947 2,449,872 Brasch et a1 Sept. 21, 1948 FOREIGN PATENTS Number Country Date 277,347 Great Britain Dec. 7, 1928 299,735 Great Britain Oct. 30, 1928 

